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S5-95F
7.4.3
Maximum Response Time with Cyclical Program Processing
The reaction to a change in the input signal is a change in the output signal. The time between the
change in the input signal and the change in the output signal is called response time.
To determine the response time, you must know the following times:
•
Program processing time
•
Operating system runtime including the read and write cycle times of the on-board I/Os
(t
80 ms)*
Besy
•
Data cycle times of the external I/Os (number of data bits x 25 µs)
•
Delay time of the input modules ( 5 ms)
Calculating the Maximum Response Time for the Onboard I/Os
Figure 7-11 shows a schematic of the S5-95F program processing.
Delay time of the
onboard DI
OBP
read1
Program
...
processing
Input signal changes;
signal change is not
yet recognized
Figure 7-11. Response Time of the Onboard I/Os (Worst Case)
You calculate the maximum response time T
the onboard I/Os as follows:
T
=
OB1 response, OBP
+1 x operating system runtime (80 ms)*
+1 x delay time of the input modules (5 ms)
Expressed in OB1 cycles, the following applies:
T
=
OB1 reponse, OBP
+ 1 x delay time of the input modules (5 ms)
=
The integrated cycle time statistics (see section 15.7) are an aid enabling you to initially assess the
cycle time.
* Times increase in the case of loading through interrupts or programmer operation (see section 7.4.2).
EWA 4NEB 812 6210-02
OBP
OBP
write1
...
ExP
Besy
2 x program processing time
2 × OB1 cycle time
- 1 x operating system runtime (80 ms)*
2×OB1 cycle time - 75 ms*
ExP:
Besy:
OBP
: Read cycle of the onboard I/Os
read
OBP
: Read cycle of the onboard I/Os
write
OBP
read2
write2
Program
...
processing
Besy
Input signal change
is recognized during
OBP
read2
with cyclical program processing via
OB1 response, OBP
Introduction to STEP 5
Data cycle of external I/Os
Operating system
OBP
read3
Program
ExP
processing
Response to input signal
change during OBP
write2
t
7-23
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